1. Field of the Invention
The present invention relates to a symbol displaying unit used for a game machine of a slot machine, a Japanese upright pinball machine, and so forth. In particular, the present invention relates to a symbol displaying unit in which a reel having symbols arranged on an outer periphery thereof is driven by a stepping motor.
2. Description of the Related Art
A slot machine using a symbol displaying unit is well known from Japanese Patent Laid-Open Publication No. 6-39085 (Japanese Patent No. 2,920,027) and so forth. In such a symbol displaying unit, nine reels having symbols arranged on outer peripheries thereof are disposed in a three-by-three matrix, and the respective reels are driven by an individual motor. When a start button of the slot machine is operated after putting a certain number of tokens into the slot machine, the symbol displaying unit is activated to simultaneously rotate the nine reels. After that, a stop button is operated to stop the reel. Alternatively, the reels are stopped based on a signal outputted from a random timer. When a specified symbol combination are obtained on any one of judgement lines, it is judged to be a hit. Incidentally, the judgement lines are, for instance, three vertical lines, three horizontal lines and two diagonal lines which are set so as to combine three reels straightly. When the hit occurs, the tokens are paid out in accordance with a number of the invested tokens and a hit combination.
The above symbol displaying unit of the nine-reel type attached to the slot machine is utilized in a recent Japanese upright pinball machine called as xe2x80x9cpachinkoxe2x80x9d, such as described in Japanese Patent Laid-Open Publication No. 9-266979. In this pinball machine, the reels are simultaneously rotated when a game ball enters a predetermined start hole. After the reels have stopped, an extra game unit called xe2x80x9cattackerxe2x80x9d is opened if the hit occurs. While the attacker is opened, almost all of the game balls flowing on a game board enter the attacker. When a predetermined number of the game balls enter the attacker, this attacker is briefly closed, and then is opened again. The operation of the attacker is repeated within an extent of sixteen times, for example. Thus, a player can obtain a large number of game balls when the hit occurs on the symbol displaying unit.
In the slot machine and the pinball machine described above, a pay-out ratio greatly fluctuates in accordance with a frequency of the hit occurring on the symbol displaying unit. In view of this, probability of hit occurrence is controlled by a microcomputer. When the symbol displaying unit is activated, the microcomputer extracts a certain number by using a random-number generator, and controls the motor of the reel so as to satisfy a result corresponding to the extracted number. Extraction of the number is performed under a predetermined probability of the hit occurrence. For the purpose of controlling the motor easily, a stepping motor is utilized as the motor for driving the reel. Based on a number of drive pulses supplied to the stepping motor, stop control of each reel is performed.
Meanwhile, the stepping motor is rotated by unit step angle whenever the drive pulse is supplied thereto. A number of steps necessary for one rotation is fixed. In case the number of steps is small, the step rotation of the reel is found out by a player when a rotational speed of the stepping motor is decreased for stopping the reel. In this case, the player is likely to have a strange feeling. This problem may be improved by using the stepping motor whose unit step angle is small, or whose step number for one rotation is large. However, such a stepping motor has a large size and is expensive so that it is difficult, because of a space for attachment and so forth, to use this stepping motor for the symbol displaying unit having nine reels arranged in the three-by-three matrix. Especially, it is difficult to be employed in the symbol displaying unit used for the pinball machine.
In the meantime, such as described in the foregoing Publication No. 9-266979, is well known a structure in which a gear fixed to a drive shaft of the stepping motor is meshed with an internal gear formed on an inner periphery of a rotary bearing. The gear of the drive shaft has a small number of teeth, and the internal gear of the rotary bearing has a large number of teeth. In this structure, the rotation of the stepping motor is transmitted to the reel in a reduction state. For the purpose of making the low-speed step rotation inconspicuous under usage of one-pair gears, it is required to increase the teeth number of the internal gear. Thus, it is necessary to enlarge the reel. Moreover, since the gear fixed to the drive shaft of the stepping motor is meshed with the internal gear of the reel in a state that the reel is rotatably supported by a fixed supporting shaft, there arise problems in that a number of parts for constituting a reel assembly increases, and in that assembling these parts becomes complicated. Further, since driving force is transmitted at a position separated from the rotational center of the reel, there arises another problem in that the rotation of the reel is likely to be biased in accordance with repetition of usage.
In view of the foregoing, it is a primary object of the present invention to provide a symbol displaying unit used for a game machine in which a reel can be downsized.
It is a second object of the present invention to provide a symbol displaying unit used for a game machine in which a reel may be smoothly rotated, using a stepping motor whose step number is small.
In order to achieve the above and other objects, the symbol displaying unit according to the present invention comprises a stepping motor, in a motor case of which at least two pairs of reduction gear mechanisms are contained.
The stepping motor includes a drive shaft and an output shaft. The drive shaft is integrally rotated with a rotor of the stepping motor, and the output shaft projects to the outside of the motor case. A rotation of the drive shaft is transmitted to the output shaft in a reduced state by the reduction gear mechanisms. Further, the motor case is disposed inside a reel so as to secure the output shaft to the reel.
The top of the output shaft is provided with a reel attaching portion having a contour of a non-circular shape. Meanwhile, one side of the reel is integrally formed with an attachment portion, an inner shape of which corresponds to the contour of the reel attaching portion of the output shaft. When fixing the reel to the output shaft, the reel attaching portion of the output shaft is fitted into the attachment portion of the reel. Then, a central portion of the reel is fastened to the top of the output shaft with a screw.
According to the present invention, the rotation of the drive shaft is transmitted to the output shaft in a considerably reduced state by at least two pairs of the reduction gear mechanisms contained in the motor case. Thus, it is not necessary to extremely increase the step number of the stepping motor itself. In virtue of this, the reel can be smoothly rotated although the reel is directly connected to the output shaft of the stepping motor. Since it is not necessary to increase the step number of the stepping motor, the rotor and the stator of the stepping motor may be downsized. Owing to this, the motor case as a whole is disposed inside the reel without increasing a diameter of the reel so that the whole of the symbol displaying unit may be effectively downsized.